Descriptions

The coastal circulation in the Santa Barbara Channel (SBC) and the southern central
California shelf is described in terms of three characteristic flow patterns. The upwelling
pattern consists of a prevailing equatorward flow at the surface and at 45 m depth, except in
the area immediately adjacent to the mainland coast in the SBC where the prevailing
cyclonic circulation is strong enough to reverse the equatorward tendency and the flow is
toward the west. In the surface convergent pattern, north of Point Conception, the surface
flow is equatorward while the flow at 45 m depth is poleward. East of Point Conception,
along the mainland coast, the flow is westward at all depths and there results a convergence
at the surface between Point Conception and Point Arguello, with offshore transport over a
distance on the order of 100 km. Beneath the surface layer the direction of the flow is
consistently poleward. The relaxation pattern is almost the reverse of the upwelling
pattern, with the exception that in the SBC the cyclonic circulation is such that the flow
north of the Channel Islands remains eastward, although weak. The upwelling pattern is
more likely to occur in March and April, after the spring transition, when the winds first
become upwelling favorable and while the surface pressure is uniform. The surface
convergent pattern tends to occur in summer, when the wind is still strong and persistently
upwelling favorable, and the alongshore variable upwelling has build up alongshore
surface pressure gradients. The relaxation pattern occurs in late fall and early winter, after
the end of the period of persistent upwelling favorable winds.